Medical diagnoses utilizing an electronic endoscope have widely been practiced in the medical field these days. The electronic endoscope has an imaging device like a CCD, which is built in an end of an elongated probing portion that is introduced into a body cavity, so that the CCD takes an image signal from an internal body site. The image signal is processed in a processor, to display an image of the internal body site, called an endoscopic image, on a monitor.
The electronic endoscope and the processor are usually connected to each other through a signal cable. Also, wireless electronic endoscopes systems have been suggested, for example, in Japanese Laid-open Patent Application Nos. Sho 60-48011 and 2001-046334. In the wireless electronic endoscope system, the electronic endoscope is provided with a modulator and a sender for sending the modulated signal as an electric wave, whereas the processor is provided with a receiver for receiving the electric wave and a demodulator for demodulating the modulated signal. Because the signal is communicated by way of the electric wave, the signal cable is unnecessary, so the handling of the wireless electronic endoscope is superior to those using the signal cable.
In addition to the above-mentioned advantage that the signal cable does not give limit to the handling of the electronic endoscope, and thus the workability is improved, the wireless electronic endoscope system has another advantage. Since there is not any electric connection between the electronic endoscope and the processor, it is unnecessary to maintain a high dielectric strength voltage of about 4 kV between a patient circuit and a secondary circuit, while such a high dielectric strength voltage is necessary for the conventional electronic endoscope system using the signal cable.
The electronic endoscope is also provided with many kinds of control switches, including a freeze switch for capturing a still image from an endoscopic image, and a movie-recording switch for recording motion pictures of the body site.
In the conventional wireless electronic endoscope, control signals entered through the control switches are sent to the processor using an electric wave of a different frequency band from the electric wave for sending the endoscopic image. In practice, it is usual to install a number of electronic endoscope systems together in a specific treatment room in a hospital. Therefore, if an individual electronic endoscope system occupies many working frequency bands, interference can occur between the equipments. To avoid the interference, the number of systems allowed to install in the same room is limited.